public void AllMetrics_SampleData_Recorded()
        {
            const int NumberOfItems = 42;
            var errors = new KeyValuePair<string, Exception>[]
            {
                new KeyValuePair<string, Exception>("1", new Exception()),
                new KeyValuePair<string, Exception>("2", new ArgumentException()),
                new KeyValuePair<string, Exception>("3", new KeyNotFoundException())
            };

            var statistics = new InMemoryTransferStatistics(ErrorDetailsProviderMock.Instance);

            statistics.Start();

            for (var index = 0; index < NumberOfItems; ++index)
                statistics.AddTransferred();

            foreach (var error in errors)
                statistics.AddError(error.Key, error.Value);

            statistics.Stop();

            var result = statistics.GetSnapshot();

            Assert.IsNotNull(result, TestResources.NullStatisticsSnapshot);
            Assert.AreNotEqual(TimeSpan.Zero, result.ElapsedTime, TestResources.StatisticsElapsedTimeIsEmpty);
            Assert.AreEqual(NumberOfItems, result.Transferred, TestResources.StatisticsInvalidTransferredCount);
            Assert.AreEqual(errors.Length, result.Failed, TestResources.StatisticsInvalidFailedCount);
            CollectionAssert.AreEquivalent(errors.ToDictionary(e => e.Key, e => ErrorDetailsProviderMock.Instance.Get(e.Value)), result.GetErrors().ToArray(),
                TestResources.StatisticsInvalidErrors);
        } 
        public async Task ExecuteAsync_SampleData_StatisticsPopulated()
        {
            const int NumberOfItems = 10;
            const int ThrowAfter = 5;

            var action = new DataTransferAction();

            var sourceData = SampleData.GetSimpleDataItems(NumberOfItems);

            var transferredCount = 0;
            var sinkMock = new DataSinkAdapterMock(i =>
                {
                    if (++transferredCount > ThrowAfter)
                        throw new Exception();
                });

            var statistics = new InMemoryTransferStatistics(ErrorDetailsProviderMock.Instance);
            statistics.Start();
            using (var source = new DataSourceAdapterMock(sourceData))
            using (var sink = sinkMock)
                await action.ExecuteAsync(source, sink, statistics, CancellationToken.None);
            statistics.Stop();

            var receivedData = sinkMock.ReceivedData;

            Assert.IsNotNull(receivedData, TestResources.NullDataInSink);
            Assert.AreEqual(ThrowAfter, receivedData.Count(), TestResources.InvalidNumberOfDataItems);

            var resultStatistics = statistics.GetSnapshot();
            Assert.AreEqual(ThrowAfter, resultStatistics.Transferred, TestResources.StatisticsInvalidTransferredCount);
            Assert.AreEqual(NumberOfItems - ThrowAfter, resultStatistics.Failed, TestResources.StatisticsInvalidFailedCount);
            Assert.AreNotEqual(TimeSpan.Zero, resultStatistics.ElapsedTime, TestResources.StatisticsElapsedTimeIsEmpty);

            var resultExceptions = resultStatistics.GetErrors();
            Assert.IsNotNull(resultExceptions, TestResources.NullTransferExceptions);
            Assert.AreEqual(NumberOfItems - ThrowAfter, resultExceptions.Count, TestResources.InvalidNumberOfTransferExceptions);
        }